Abstract Body: Background: People with stroke are at high risk of dementia. There have been reductions in stroke case fatality and disability but temporal trends in the incidence and absolute burden of post-stroke dementia have not been described.

Methods: We did a population-wide analysis of over 15 million people in Ontario, Canada between 2002-2022. Using linked administrative databases, we identified all 90-day dementia-free survivors of first acute ischemic stroke or intracerebral hemorrhage (ICH). We evaluated dementia incidence from 90-days after stroke onwards using a validated definition which included hospitalization, physician claims, and dementia medications. We calculated 1-year and 5-year incidence of dementia as percentages and per 100 person-years for each fiscal year, age-/sex-standardized by the 2002 population and with follow-up until March 2022. We stratified incidence trends by sex, stroke type, and severity (90-day home time of <60 days indicating moderate-severe stroke). We described trends in absolute number of people with post-stroke dementia, stratified by sex, and used linear regression to evaluate significance.

Results: We identified 175,980 people with acute stroke surviving dementia-free to 90 days. From 2002-2021, there was modestly decreasing 1- and 5-year dementia incidence, primarily occurring from 2011 onwards (Figure 1). 5-year dementia decreased by an absolute change of -2.4% (15.5% to 13.1%) and a relative change of -15%. However, there was an increase in the number of people surviving with stroke (Figure 1A-B), so the absolute number of people with post-stroke dementia remained stable or increased over time (Figure 2). Women had higher age-standardized dementia incidence than men, but no difference in trends (Figure 3A-B). There was decreasing dementia incidence for ischemic stroke but no significant change for ICH (Figure 3C-D). Those with 90-day home time <60 days had twice the incidence of dementia compared to those with >60 days, with no change over time (Figure 3E-F).

Conclusion: In this large, population-wide study from 2002-2022, a modest decrease in post-stroke dementia incidence was offset by increasing numbers of stroke survivors and resulted in a rising absolute burden of post-stroke dementia. Those with more severe stroke had 2-fold higher dementia rate which did not change over time despite improvements in stroke care. New strategies are needed to address the persistent and increasing burden of post-stroke dementia.